The exemplary embodiments described herein relate to optical analysis systems and methods for analyzing fluids.
Cementing operations are often used in wellbores for, inter alia, supporting casings and liners, providing zonal isolation, and protecting the casing from corrosive formation fluids. In such operations, it is often important to precisely know the location, characteristics, and setting status of cement slurries as they circulate and set in wellbores or other annuli therein. In situ analysis of cement slurries during cementing operations is often not achievable with conventional monitoring systems, which are incapable of operation in extreme environments such as downhole applications. Accordingly, the location, characteristics, and setting status of cement slurries are often required to be extrapolated from laboratory data, calculations of volumes to be filled, and calculations based on the conditions in the wellbore (e.g., temperature).
After the cementing operation has completed, the location, characteristics, and setting status of a cement slurry (or set cement) can be analyzed via logging techniques, which are time-consuming and costly. For example, if the cementing operation was successfully performed (e.g., the proper locations were cemented) and the cement is sufficiently set, subsequent subterranean operations can be performed (e.g., drilling operations, fracturing operations, completion operations, and the like). However, if an aspect of the cementing operation was incorrect, remedial operations are often necessary.
For example, if the cement is not sufficiently set, the operator allows for additional setting time and then runs another logging operation, which further contributes to costs and nonproductive time.
In another example, if too much cement slurry was added, a drill-out operation may be required, which is particularly prevalent in reverse cementing where the cement is pumped from the annulus side. In other instances, if too little cement slurry was added, another cementing operation may be needed.
These issues can be especially complex in normal primary cementing operations where the cement slurry is pumped down the casing and up the annulus. Generally, the cement slurry formulations are designed so that the ‘lead’ slurry (i.e., uppermost slurry after placement in the annulus) is of lower density than the ‘tail’ slurry that is the bottommost slurry placed near the bottom of the annulus. Proper placement of the ‘lead’ slurry behind casing and the sufficient setting of the cement near the casing shoe (i.e., near the bottom of the casing) are important for the casing to withstand pressures of the initial pressure test and subsequent drilling that are performed.
In other cementing operations, e.g., some remedial operations to plug thief zones, two fluids are utilized that, when contacted, viscosify and plug high permeability regions in the wellbore. Pumping calculated volumes is often insufficient to assure operation efficacy, which can lead to additional remedial operations and the use of high volumes of expensive fluids. Accordingly, in situ monitoring of the location of each of these fluids may reduce the cost and time associated with such remedial cementing operations.
As a whole, cementing operations are often performed multiple times during the lifetime of a well. Therefore, in situ analysis of cement slurries and/or set cements may have a compounding effect on reducing the cost and time associated with the drilling and maintenance of a well.